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DR Medhat MRCP

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Relative afferent pupillary defect (=Marcus-Gunn pupil)<br />

- It is a medical sign observed during the swinging-flashlight test in which the patient's<br />

pupils constrict less (therefore appearing to dilate) when a bright light is swung from<br />

the healthy eye to the affected eye.<br />

- It is caused by a lesion anterior to the optic chiasm (i.e. optic nerve) or retina.<br />

• Causes<br />

Retina: detachment<br />

Optic nerve : optic neuritis e.g. multiple sclerosis<br />

Pathway of pupillary light reflex<br />

Afferent: retina → optic nerve → lateral geniculate body → midbrain<br />

Efferent : Edinger-Westphal nucleus (midbrain) → oculomotor nerve<br />

Swinging-flashlight test<br />

Pathway of papillary light reflex<br />

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